Thermal responsive devices with ambient temperature compensation have been known heretofore. For example, O. S. Field Pat. No. 2,109,169, dated Feb. 22, 1938, shows a thermal operated circuit controlling device having a bimetal strip mounted at its lower end in a glass tube and having a compensating bimetal strip welded to its upper end with the two strips oriented to deflect in opposite directions in response to temperature change thereby to provide ambient temperature compensation. The lower bimetal strip is heated by a coil of resistance wire. Varying the pressure of gas in the tube causes change in the rate of dissipation of heat, the gas being the heat sink, so as to increase or decrease the time required to operate the contacts for a given heating current. While such prior thermal responsive devices have been useful for their intended purposes, this invention relates to improvements thereover.